Aging is a functional, structural and biochemical process that occurs continuously throughout the life of human beings. Aging occurs throughout the cells and tissues of the human body, displays a decrease in metabolic rate, an increase in diseases, a decrease in adaptability and the like, and ultimately leads to the death of the cells and the whole of tissues of the human body. Theories explaining the processes and causes of aging are broadly divided into the genetic theories (Chung. H. Y. et al., Kor. J. Gerontol., 2:1, 1992) and the wear-and-tear theories (Chung. H. Y. et al., Kor. J. Gerontol., 2:1, 1992). The wear-and-tear theories suggest that the cells of organisms lose their functions with the passage of time or due to the accumulation of harmful substances. Among these explanations, the most plausible theory is the free radical theory suggesting that free radicals which are produced through human metabolic processes, radiation exposure, viruses, heavy metals and air pollution form highly toxic substances, thereby stimulating aging and causing various diseases related to aging.
Free radicals are substances having one unpaired electron in the outermost orbit and their structure is highly unstable and reactive because they tend to be stabilized by receiving electrons. Particularly, free radicals which are derived from oxygen are termed “reactive oxygen species”, and these reactive oxygen species react with proteins, lipids, carbohydrates and the like to cause lipid peroxidation, DNA damage, protein oxidation and the like, thereby causing damage intracellular structures and ultimately causing the death of cells. Particularly, these reactive oxygen species increase arterosclerosis, Alzheimer's disease and blood homocysteine levels by involving inflammatory processes as a cause of vascular aging.
Oxygen-related toxic substances in the human body are referred to as reactive oxygen species (ROS). Examples of ROS include free radicals, such as superoxide, hydroxyl, peroxyl, alkoxyl and hydroperoxyl, and non-free radial radicals, such as hydrogen peroxide, hypochlorous acid, ozone, singlet oxygen, and peroxynitrite. Among these reactive oxygen species, superoxide free radicals have been most frequently studies and play an important role (Fridovich L., Science, 201:175, 1978).
During the progression of aging, ROS generated in cellular mitochondria becomes a target indicating oxidative damage (Lesnefsky, E. J. & Hoppel, C. L. Arch. Biochem. Biophys. 420, 287, 2003). There are many reports that the free radical theory regarding intracellular oxygen radicals has much correlation with aging-related oxidative stress and aging-related diseases caused thereby (Finkel, T. & Holbrook, N. J., Science 408; 239, 2000) and there are also reports that such oxidative stress play an important role in inducing senescence (Chen Q. et al., Proc. Natl. Acad. Sci. U.S.A. May 9; 92(10):4337, 1995; Packer L. & Fuehr K., Nature, 267(5610):423, 1977). Such oxidative stress is a term used to describe damage to cells caused by the oxidation of macromolecules by an increasing level of reactive oxygen species and reduced antioxidant reserve (Thomas C. & Squier, Experimental Gerontology, 36; 1539, 2001).
Aged cells which are in the progression of replicative senescence can produce ROS at higher levels compared to young cells and also produce toxic byproducts, such as superoxide, hydrogen peroxide, hydroxyl radicals and the like during a normal metabolic process. According to the results of experiments on old individuals or old test animals, tissues accumulate oxidative damage to their DNAs, proteins and lipids (Chen, Ann. N. Y. Acad. Sci., 908:111, 2000). ROS, and particularly, hydroxyl radical, attacks DNA and causes the formation of 8-oxo-2′-deixyguanosine and other potent mutagenic adducts, and the ratio of ROS in each species is associated with life-span and that means it is the decisive factor in defining the rate of aging and various diseases related to aging (Finkel & Holbrook, Nature, 408(6809): 239, 2000).
In 1961, Hayflick and Moorhead first reported that the replicative potential of young cultured cells decreases as the number of divisions increase, and ultimately the cells lose proliferative potential and have a “doubling limited” which the growth condition is over. Since then, ROS has been used to define the senescence-related molecular changes of human cells as experimental models for in vitro senescence and intracellular senescence in human fibroblasts (HAYFLICK L. & MOORHEAD P. S., Exp. Cell Res., 25: 585, 1961).
All aerobic organisms, including humans, fundamentally have a self-defense mechanism against injury caused by reactive oxygen species which always occur during an energy metabolic process that uses oxygen, the production of reactive oxygen species exceeding the defense capability of tissues causes various adult diseases, including arthritis, disorders of the cardiovascular system, and dementia (Halliwell et al., Drugs, 42:569, 1991; Fukuzawa et al., J. Act. oxyg. Free Rad., 1:55, 1990).
Reactive oxygen species which are frequently called harmful oxygen species include superoxide anion (O2−) which is singlet oxygen produced by oxidation-reduction of the most stable triplet oxygen (3O2); hydrogen peroxide (H2O2), hydroxyl radical (.OH) as unpaired free radicals, and these cause diseases by damaging factors of the immune system, such as proteins, DNA, enzymers and T cells (Regnstrom et al., Lancet., 16:1183, 1992; Gey et al., Am. Ac. J. Clin. Nutr., 53:326, 1991).
For this reason, studies on the development of antioxidants have been actively conducted and, as a result, many antioxidants are known, including preventive antioxidant enzymes, such as superoxide dismutase, catalase and glutathioneperoxidase, natural antioxidants, such as vitamin E, vitamin C, carotenoid and glutathione, and synthetic antioxidants, such as t-butyl-4-hydroxyanisole (BHA) and 3,5-(t-butyl)-4-hydroxytoluene (BHT). However, the antioxidant enzymes show a decrease in the defense ability against reactive oxygen species as people get older, and the synthetic antioxidants are known to have mutagenecity and toxicity. For these reasons, it is urgently required to develop more stable and potent natural antioxidants (Hatano et al., Natural Medicines, 49:359, 1995; Masaki et al., Biol. Pharm. Bull, 18:162, 1995).
Meanwhile, inflammation is a local response which appears against injury sites to initiate the removal of invasion of pathogens or damaged tissues. Despite its positive role, inflammation became one of the most general pathogenic mechanisms for human diseases. The production of nitric oxide (NO) in activated monocytes and macrophages initiates a potent inflammatory response and is most important in an initial immune response to bacterial pathogens (Bogdan C., Nat. Immunol., 2:907, 2001).
When there is a damage to a tissue (cell) or an infection by a foreign substance (e.g., bacteria, fungi, viruses, various allergy-inducing materials), it usually entails an inflammatory response expressed as a series of complex physiological responses such as activation of enzyme, secretion of inflammation-mediating materials, infiltration of body fluid, cell movement, and damage to tissues that are related to various inflammation-mediating factors and immunocytes in local blood vessels and body fluid, and as external symptoms such as erythema, edema, pyrexia and pain. For normal persons, inflammatory responses remove external sources of infection, reproduce damaged tissues, and recover the function of organisms, but when an antigen is not removed or inflammatory responses occur excessively or continuously due to intrinsic substances, inflammatory responses stimulate damage to mucosa and, as a result, in some cases, cause diseases such as cancer. Accordingly, there has been a need to develop natural anti-inflammatory agents which can prevent excessive and continuous inflammatory responses without causing side effects.
Therefore, the present inventors have made many efforts to develop natural material-derived compositions which minimized side effects compared to existing antioxidants and anti-inflammatory agents and have excellent antioxidant activity and anti-inflammatory activity. As a result, the present inventors have found that a Taxus cambium- or procambium-derived cell line and an extract thereof have excellent inhibitory effects against aging and inflammation, thereby completing the present invention.